Bearing apparatus for supporting pinion shaft and pinion shaft support apparatus

ABSTRACT

A double row angular contact ball bearing with vertex of contact angles outside of bearing  6  is employed for supporting a pinion shaft  5 , and an internal space of the bearing  6  is also sealed with seals  20  and  30  equipped at both ends thereof in a shaft direction, so that grease is filled in this sealed bearing internal space. In this case, oil being used for a target apparatus for use of the pinion shaft  5  is not introduced inside the bearing  6 , so that problems which have been generated in a conventional example where said oil has been introduced inside the bearing  6  can be cleared up.

FIELD OF THE INVENTION

The present invention relates to a bearing apparatus for supporting apinion shaft and a pinion shaft support apparatus.

DESCRIPTION OF THE PRIOR ART

As a bearing apparatus for supporting a pinion shaft for rotatablysupporting the pinion shaft incorporated in a transfer, a differential,or the like mounted on a vehicle, a bearing apparatus using two singlerow tapered roller bearings (refer to Japanese Patent ApplicationLaid-Open No. 10-220468) and a bearing apparatus in which a single rowtapered roller bearing and a single row angular contact ball bearing areintegrated (refer to Japanese Patent Application Laid-Open No. 53-74653)are conventionally employed.

For both of the bearing apparatuses for supporting the pinion shaft asdescribed above, a pinion gear side thereof is in an opened statewithout being provided with a seal, and lubrication is performed usingoil accommodated inside the transfer or the differential.

In the transfer or the differential described above, torque reductionfor the pinion shaft has been required in recent years.

However, in both of the bearing apparatuses for supporting the pinionshaft described above, since the tapered roller bearing is employed,there exists a limitation in torque reduction.

In addition to that, in the case of the bearing apparatus for supportingthe pinion shaft being used for the transfer, since a central shaft lineof the pinion shaft is arranged upper than a central position of atransfer case, it may be pointed out that the oil in the case does noteasily reach the inside of the bearing apparatus for supporting thepinion shaft. For that reason, a shape of the transfer case must bedevised so that the oil may be efficiently introduced into the inside ofthe bearing, thereby forcing enlargement of the case.

On the other hand, in the case of the bearing apparatus for supportingthe pinion shaft being used for the differential, since a central shaftline of the pinion shaft is arranged lower than a central position ofthe transfer case, the oil is introduced excessively, so that there ispointed out disadvantages in achieving torque reduction such thatstirring resistance of the oil is increased and foreign substances inthe oil are bit between a tapered roller and a raceway surface.

SUMMARY OF THE INVENTION

A bearing apparatus for supporting a pinion shaft of the presentinvention is a bearing apparatus for supporting a shank portion of apinion shaft having a pinion gear at one end, and is a double rowangular contact ball bearing with vertex of contact angles outside ofbearing, wherein grease is filled in a bearing internal space sealedwith seals equipped at both ends in a shaft direction.

In this case, rolling resistance of the double row angular contact ballbearing with vertex of contact angles outside of bearing is smallercompared with that of a tapered roller bearing, thereby giving theadvantage of reducing torque. Moreover, the double row angular contactball bearing with vertex of contact angles outside of bearing isconfigured so as to be sealed with the seals to be lubricated by thegrease, so that oil in a target apparatus for use of the pinion shaft isnot introduced inside the bearing, thereby enabling to clear up theproblems relevant to the oil which have been pointed out in theconventional example.

Incidentally, the double row angular contact ball bearing with vertex ofcontact angles outside of bearing described above may comprise a singleouter ring having double raceway surfaces in a shaft direction and alsohaving counter bores at both ends thereof in the shaft direction, afirst inner ring having a single raceway surface pairing with oneraceway surface of this outer ring and also having a counter bore at aninner edge in the shaft direction, a second inner ring having a singeraceway surface pairing with the other raceway surface of said outerring and also having a counter bore at an inner edge in the shaftdirection, and a plurality of balls interposed between said doubleraceway surfaces of said outer ring and each of said raceway surfaces ofsaid two inner rings.

A contact angle of said ball may be set to be preferably not less than30 degrees and not more than 45 degrees. Preferably, a radius ofcurvature of each raceway surface of said outer ring may be set to benot less than 51.0% and not more than 52% of the ball diameter, and aradius of curvature of the raceway surface of each of said inner ringmay also be set to be not less than 50.2% and not more than 51.2% of theball diameter, respectively. When the contact angle of the double rowangular contact ball bearing with vertex of contact angles outside ofbearing, and the radius of curvature of the raceway surface arespecified so as to be different from those of a typical standard itemlike this, load carrying capacity and durability can be improved.

An outer peripheral portion of said each seal is preferably fixed to thetwo counter bores of said outer ring, and may be configured so as tocomprise a lip portion at an inner periphery having a shape forcontacting to each shoulder portion of said two inner rings, and beingable to be opened towards the outside of the bearing. In this case, theseal is a particularly superior type for preventing foreign substancesfrom entering the inside from the outside of the bearing, thereby givingthe advantage of stabilizing a behavior of the grease filled inside thebearing.

Preferably, the lip portion of the seal arranged at a pinion gear sideis compulsorily pressed to the shoulder portion of said inner ring bymeans of a spring ring.

An air flow portion for communicating the inside with the outside ofsaid bearing is preferably formed in the seal arranged on acounter-pinion gear side. In this case, an internal pressure thereof islowered rather than an external pressure as the bearing is cooled to alow temperature state from a high temperature state, so that a pressuredifferential between the inside and the outside of the bearing may bereduced by an air flow function between the inside and the outside ofthe bearing by means of the air flow portion formed in the seal on thecounter-pinion gear side. Thus, there may be now prevented a generationof a phenomenon where the lip portion of the seal on the counter-piniongear side is strongly pressed to the shoulder portion of the inner ring(so-called sticking phenomenon).

A pinion shaft support apparatus of the present invention comprises apinion shaft having a pinion gear at one end and having a screw shaftportion at the other end, a double row angular contact ball bearing withvertex of contact angles outside of bearing attached to an outside of ashank portion of said pinion shaft, a nut which is screwed and fixedonto said screw shaft portion of said pinion shaft and integrates saiddouble row angular contact ball bearing with vertex of contact anglesoutside of bearing with said pinion shaft, wherein said double rowangular contact ball bearing with vertex of contact angles outside ofbearing is filled with grease in a bearing internal space sealed withseals equipped at both ends in a shaft direction.

In this case, the double row angular contact ball bearing with vertex ofcontact angles outside of bearing is equivalent to the bearing apparatusfor supporting the pinion shaft mentioned above, thereby making itpossible to obtain a function and an effect in a matter similar to theabove. Moreover, the pinion shaft and the double row angular contactball bearing with vertex of contact angles outside of bearing as thebearing apparatus for supporting the pinion shaft are unitized, so thattime and effort in incorporating it in a target for use is reduced,thereby making it possible to improve assembly performance.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view showing a pinion shaft supportapparatus according to one embodiment of the present invention;

FIG. 2 is an enlarged view of an upper half of double row angularcontact ball bearing with vertex of contact angles outside of bearingshown in FIG. 1;

FIG. 3 is a perspective view showing a tail end seal in FIG. 1;

FIG. 4 is a perspective view showing an application of the head end sealin FIG. 1; and

FIG. 5 is a perspective view showing an application of the tail end sealin FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1 through FIG. 3, description will be made of apreferred embodiment of the present invention. A pinion shaft supportapparatus 1 illustrated in the drawings is incorporated in a case 2 of atransfer or a differential, and comprises a pinion shaft 5, a double rowangular contact ball bearing with vertex of contact angles outside ofbearing 6, a coupling sleeve 7, and a nut 8. Incidentally, the doublerow angular contact ball bearing with vertex of contact angles outsideof bearing 6 is equivalent to a bearing apparatus for supporting apinion shaft.

A pinion gear 5 b is formed at one end of a shank portion 5 a of thepinion shaft 5 in a shaft direction, and a screw shaft portion 5 c isformed at the other end thereof in the shaft direction, respectively.The double row angular contact ball bearing with vertex of contactangles outside of bearing 6 is attached to the outside of the shankportion 5 a of this pinion shaft 5, and the coupling sleeve 7 isspline-fitted thereto, and the nut 8 is screwed onto the screw shaftportion 5 c of the pinion shaft 5, so that in a state where a preload isapplied to the double row angular contact ball bearing with vertex ofcontact angles outside of bearing 6, the double row angular contact ballbearing with vertex of contact angles outside of bearing 6 is integratedwith the pinion shaft 5, and the pinion shaft support apparatus 1 isthus configured.

The coupling sleeve 7 is connected with a propeller shaft (not shown) ofa vehicle.

The coupling sleeve 7 is generally called an output flange whichproduces a turning force of the pinion shaft 5 to said propeller shaftin the case of the transfer, and called a companion flange whichsupplies the turning force of said propeller shaft into the pinion shaft5 in the case of the differential.

The pinion shaft support apparatus 1 is rotatably supported at its shankportion 5 a of the pinion shaft 5 by a through hole 2 a of the case 2via the double row angular contact ball bearing with vertex of contactangles outside of bearing 6 in a state of arranging the pinion gear 5 binside the case 2, and the double row angular contact ball bearing withvertex of contact angles outside of bearing 6 receives an axial load anda radial road which act on the pinion shaft 5.

Description will be made of the double row angular contact ball bearingwith vertex of contact angles outside of bearing 6 in detail.

The double row angular contact ball bearing with vertex of contactangles outside of bearing 6 comprises a single outer ring 10, two innerrings 11 and 12, a plurality of balls 13, and two cage rings 14 and 15.

The outer ring 10 has double raceway surfaces 10 a and 10 b in the shaftdirection, and also has counter bores 10 c and 10 d on both ends thereofin the shaft direction and is further comprised of a flange 10 eradially extending outwardly at an outer diameter portion. This outerring 10 is fitted into the through hole 2 a of the case 2, and itsflange 10 e is fixed to the case 2 with a bolt 9. An O ring 3 isinterposed in a fitting surface between the outer ring 10 and thethrough hole 2 a of the case 2.

A first inner ring 11 has a single raceway surface 11 a pairing with oneraceway surface 10 a of the outer ring 10, and also has a counter bore11 b at an inner edge in the shaft direction. A second inner ring 12 hasa single raceway surface 12 a pairing with the other raceway surface 10b of the outer ring 10, and also has a counter bore 12 b at an inneredge in the shaft direction. These two inner rings 11 and 12 areattached to the outside of the shank portion 5 a of the pinion shaft 5.

The balls 13 are interposed between the double row raceway surfaces 10 aand 10 b of the outer ring 10, and each of the raceway surfaces 11 a and12 a of the two inner rings 11 and 12. The cage rings 14 and 15 arecalled a crown type, and circumferentially arrange at approximatelyequal intervals each of said plurality of balls 13 which are arranged indouble rows.

The double row angular contact ball bearing with vertex of contactangles outside of bearing 6 is designed so as to be different from atypical standard item in view of an operating condition in the transferor the differential. Hereafter, description will be made of it indetail.

Now, in the case of the double row angular contact ball bearing withvertex of contact angles outside of bearing of the typical standarditem, a nominal angle of contact α of the ball 13 is set to be not lessthan 20 degrees and not more than 25 degrees.

Radiuses of curvature R1 and R2 of each of the raceway surfaces 10 a and10 b of the outer ring 10 is set to be not less than 52.5% and not morethan 53% of a diameter r of the ball 13.

Radiuses of curvature R3 and R4 of the raceway surfaces 11 a and 12 a ofeach of the inner rings 11 and 12 are set to be not less than 51.5% andnot more than 52.5% of the diameter r of the ball 13.

As opposed to this, the nominal angle of contact α of the ball 13 is setto be not less than 30 degrees, and preferably in the range of not lessthan 35 degrees and not more than 45 degrees in this embodiment. Theradiuses of curvature R1 and R2 of each of the raceway surfaces 10 a and10 b of the outer ring 10 are set to be not less than 51.0% and not morethan 52% of the diameter r of the ball 13, and preferably not less than51.2% and not more than 51.8% thereof. The radiuses of curvature R3 andR4 of the raceway surfaces 11 a and 12 a of each of the inner rings 11and 12 are set to be not less than 50.2% and not more than 51.2% of thediameter r of the ball 13, preferably not less than 50.5% and not morethan 51% thereof.

If the nominal angle of contact α is thus set to be larger than atypical value described above, load capacity in an axial direction maybe increased. If the radiuses of curvature R1 through R4 are set to besmaller than the typical value described above, indentation by the ball13 may be made hard to attach to the outer ring 10 or two inner rings 11and 12. Thereby making it possible to improve load carrying capacity anddurability as the double row angular contact ball bearing with vertex ofcontact angles outside of bearing 6.

Besides making the maximum thickness of the two inner rings 11 and 12larger than that of the typical standard item, an outer diameterdimension about a bottom and an outer diameter dimension of a shoulderportion of the raceway surfaces 11 a and 12 a are set to be large asmuch as possible (those are formed to be relatively thicker than that ofthe outer ring 10), and outer diameter dimensions of the counter bore 11b and 12 b are also set to be small as much as possible. Thus, a pitchcircle diameter (PCD) of the ball 13 may be enlarged as much aspossible, thereby making it possible to increase the number of balls 13to be used and improve load carrying capacity. Furthermore, since a step(or the amount of gradation) from the raceway surfaces 11 a and 12 a tothe counter bore 11 b and 12 b is increased, an opposite annular spacebetween the outer ring 10 and two inner rings 11 and 12 may be enlarged,thereby making it possible to increase an amount of grease to beenclosed.

Furthermore, the double row angular contact ball bearing with vertex ofcontact angles outside of bearing 6 is configured so as to be lubricatednot by the oil accommodated within the case 2 but by the grease, anddescription will be made of it in the following.

In other words, both ends of the outer ring 10 in the shaft directionare equipped with contacted type seals 20 and 30, so that the oppositeannular space between the outer ring 10 and the two inner rings 11 and12 (bearing internal space) is sealed, and a predetermined amount ofgrease is then filled in this annular space (not shown).

Moreover, a slinger 40 with U section is arranged at a far outside ofthe seal 30 on the tail end. The inner peripheral portion of thisslinger 40 is fixed to an outer peripheral surface of the couplingsleeve 7 by means of a press fit, and an outer peripheral portionthereof is faced to an inner peripheral surface of a heel of the outerring 10 via a fine clearance, so that a labyrinth seal (non-contactingseal portion) is formed.

Incidentally, the seal 20 arranged on the head end (pinion gear 5 bside) is generally formed by a type called an oil seal, and in additionto that, the seal 30 arranged on the tail end (counter-pinion gear 5 bside) is formed by a type called a bearing seal. When describing this indetail, the two seals 20 and 30 described above are configured by meansof vulcanization-adhering of elastic bodies 22 and 32, such as rubber,to annular core rings 21 and 31. Said annular core rings 21 and 31 havea shape where annular plate portions 21 b and 31 b radially extendinginwardly are arranged at one end of bodies 21 a and 31 a in the shaftdirection. Moreover, said elastic bodies 22 and 32 comprises a coveringskin portion (symbol is not shown) which covers from the periphery ofthe bodies 21 a and 31 a of said annular core rings 21 and 31 to oneside of the annular plate portions 21 b and 31 b, and lip portions 23and 33 which project to an inner periphery of the annular plate portions21 b and 31 b. Incidentally, the lip portions 23 and 33 have a shapebeing able to be opened towards the outside of the bearing so as tomainly prevent foreign substances from entering from the outside of thebearing.

The bodies 21 a and 31 a of the annular core rings 21 and 31 are fittedto the two counter bores 10 c and 10 d of the outer ring 10 by a pressfit via the covering skin portion of the elastic bodies 22 and 32,respectively, thereby both of the seals 20 and 30 described above arefixed. In a state where the seals 20 and 30 are fixed like this, innerperipheries of the lip portions 23 and 33 are contacted to each shoulderportion of the two inner rings 11 and 12 in a state with a predeterminedtightly pressed force.

Moreover, the head end seal 20 described above is configured such thatthe lip portion 23 is compulsorily pressed to the first inner ring 11 bymeans of a spring ring 24, so that sealing performance is improved asmuch as possible, thereby making it possible to strongly prevent the oilin the case 2 from entering the inside of the bearing.

In the meanwhile, the tail end seal 30 described above does not employ aspring ring or the like, and an inner diameter of the lip portion 33 isonly set to be smaller than the outer diameter of the shoulder portionof the inner ring 12 by a predetermined amount, thereby the lip portion33 is contacted to the inner ring 12 by means of utilizing thisvariation of tolerance in a state where the diameter thereof isresiliently expanded.

Moreover, in the tail end seal 30, there is provided an air flow groove34 along the shaft direction at one portion of a circumference of theouter diameter portion as an air flow portion for communicating theinside with the outside of the bearing. This air flow groove 34 isarranged in the body 31 a of the annular core ring 31, and the coveringskin portion of the elastic body 32 which is put on this body 31 a isput so as to follow to an outer diameter shape of the body 31 a. In thiscase, when the double row angular contact ball bearing with vertex ofcontact angles outside of bearing 6 is cooled to a low temperature statefrom a high temperature state, an internal pressure of the bearing willbe lowered rather than an external pressure thereof, but in that case,since a pressure differential between the inside and the outside of thebearing may be reduced by means of an air flow function between theinside and the outside of the bearing caused by the air flow groove 34formed in the tail end seal 30, there can be prevented a generation of aphenomenon where the lip portion 33 at the tail end seal 30 is stronglypressed to the shoulder portion of the inner ring 12 (so-called stickingphenomenon).

Incidentally, an acrylic rubber, a heat-resistant acrylic rubber, or thelike is preferably used as the elastic bodies 22 and 32 of the seals 20and 30 described above. Said heat-resistant acrylic rubber may be anethylene acrylic rubber in which an ethylene and an acrylic ester arecombined as base of a copolymer composition.

Moreover, as for the grease filled inside the double row angular contactball bearing with vertex of contact angles outside of bearing 6, adiurea type grease or an ester type grease having a desirable affinitywith gear oil is preferably employed taking into consideration heatresistance. Specifically, a grease called, for example a tradenameKNG170 made by Japan Grease Co. Ltd., or a tradename MULTEMP SRL made byKyoudou Yusi Co. Ltd., is suitably used as this grease. The above KNG170is provided by employing a poly a olefin mineral oil as base oil, and adiurea as thickening agent, and an operating temperature limit thereofis −30 degree C. through 150 degree C. The above MULTEMP SRL is providedby employing an ester as base oil, and a lithium soap as thickeningagent, and an operating temperature limit thereof is −40 degree C.through 130 degree C.

As described above, the double row angular contact ball bearing withvertex of contact angles outside of bearing 6 is used for supporting thepinion shaft 5, so that rolling resistance thereof is reduced comparedwith that in the case of using a tapered roller bearing, therebyobtaining the advantage for achieving torque reduction. Moreover, as forthe double row angular contact ball bearing with vertex of contactangles outside of bearing 6, the nominal angle of contact α, and theradiuses of curvature R1 and R2 of the raceway surfaces 10 a and 10 b ofthe outer ring 10 and the radiuses of curvature R3 and R4 of the racewaysurfaces 11 a and 12 a of each of the inner rings 11 and 12 are madedifferent from those of the typical standard item, so that it isspecified so as to clear up an operating condition in the transfer orthe differential, thereby ensuring sufficient load carrying capacity anddurability. Moreover, the double row angular contact ball bearing withvertex of contact angles outside of bearing 6 is configured so as to besealed with the seals 20 and 30 to be lubricated with the grease, sothat the oil in the case 2 which is a target for use of the pinion shaft5 may not be introduced therein, thereby clearing up the problemsrelevant to the oil that have been pointed out in the conventionalexample. In other words, grease lubrication is employed instead of oillubrication, so that an increase in torque by oil stirring resistancecan be suppressed, and since it is necessary to form neither an oilintroduction path nor an oil return path in the case 2, or the like,reduction in size and weight of the transfer or the differential may beachieved, and in addition to that, since it is not influenced by foreignsubstances in the oil like a case of the oil lubrication, it maycontribute to a life improvement of the double row angular contact ballbearing with vertex of contact angles outside of bearing 6, and amaintenance-free improvement thereof.

Therefore, in the pinion shaft support apparatus 1 of this embodiment,torque of the pinion shaft 5 may be reduced compared with that of theconventional example, thereby making it possible to contribute to animproving in efficiency of the transfer and the differential.

In addition to this, the pinion shaft 5 and the double row angularcontact ball bearing with vertex of contact angles outside of bearing 6are unitized to configure the pinion shaft support apparatus 1 as aboveembodiment, so that time and effort in incorporating it in the case 2 ofthe transfer or the differential that is a target for use is reduced,thereby making it possible to improve assembly performance.

Another embodiment of the present invention will be described in thefollowing.

(1) As for the seal 20 on the head end described above, the coveringskin portion of the elastic body 22 is formed on the inner peripheralsurface of the body 21 a of the annular core ring 21, and the body 21 aof the annular core ring 21 is fitted into the counter bore 10 c of theouter ring 10 by means of a direct press fit as shown in FIG. 4.Incidentally, a surface of the counter bore 10 c of the outer ring 10 isfinished in smoothness by means of polishing, thereby improving sealingperformance of a fitting surface with the annular core ring 21. In thiscase, accuracy of position for fitting the seal 20 on head end may beimproved, and interference with the ball 13 can be certainly avoided.

(2) As for the seal 30 on the tail end described above, it may be madeas a configuration called the so-called pack seal combining with aslinger 50 as shown in FIG. 5. The lip portion 33 of the seal 30 iscontacted with the outer peripheral surface of the body 51 of theslinger 50 with a predetermined tightly pressed force, and in additionto that, the covering skin portion which covers the annular plateportion 31 b of the seal 30 is faced to an annular plate portion 52 ofthe slinger 50 via a fine clearance. In this case, an effect ofpreventing water from entering the inside of the bearing is improvedeven when the water is poured from the outside, and in addition to that,protection of the seal 30 can be achieved, such as being able to preventwater from directly touching to the seal 30 by means of the existence ofthe slinger 50.

(3) In the embodiment described above, in order to integrate the pinionshaft 5 with the double row angular contact ball bearing with vertex ofcontact angles outside of bearing 6, it is configured so that the nut 8may be screwed and fastened onto the screw shaft portion 5 c of thepinion shaft 5, but following configuration may be employed. In otherwords, without providing the screw shaft portion 5 c to the pinion shaft5, the counter-pinion gear 5 b side of this pinion shaft 5 is made intoa tubular type shape, and this tubular type shape portion isroll-caulked in a form of outwardly extending in the radial direction,thereby making it possible to achieve a structure for integrating thepinion shaft 5 with the double row angular contact ball bearing withvertex of contact angles outside of bearing 6 by means of this caulkingportion.

In the above bearing apparatus for supporting the pinion shaft, besidesmaking it smaller in size and light in weight, it is possible to reducetorque of the pinion shaft compared with that of the conventionalexample.

In the pinion shaft support apparatus of the present invention, besidesmaking it smaller in size and light in weight, it is possible to maketorque of the pinion shaft smaller compared with that of theconventional example and also achieve an assembly simplification to atarget for use

INDUSTRIAL AVAILABILITY

It can be used for a bearing apparatus for supporting a pinion shaft forrotatably supporting a pinion shaft incorporated in a transfer, adifferential, or the like mounted on a vehicle.

1. In a bearing apparatus for supporting a shank portion of a pinionshaft having a pinion gear at one end, the bearing apparatus forsupporting the pinion shaft, comprising: a double row angular contactball bearing with vertex of contact angles outside of bearing, whereingrease is filled in a bearing internal space sealed with seals equippedat both ends in a shaft direction.
 2. The bearing apparatus forsupporting the pinion shaft according to claim 1, wherein said doublerow angular contact ball bearing with vertex of contact angles outsideof bearing comprises a single outer ring having double raceway surfacesin a shaft direction and also having counter bores at both ends thereofin the shaft direction, a first inner ring having a single racewaysurface pairing with one raceway surface of this outer ring and alsohaving a counter bore at an inner edge in the shaft direction, a secondinner ring having a singe raceway surface pairing with the other racewaysurface of said outer ring and also having a counter bore at an inneredge in the shaft direction, and a plurality of balls interposed betweensaid double raceway surfaces of said outer ring and each of said racewaysurfaces of said two inner rings.
 3. The bearing apparatus forsupporting the pinion shaft according to claim 2, wherein a contactangle of said ball is set to be not less than 30 degrees and not morethan 45 degrees.
 4. The bearing apparatus for supporting the pinionshaft according to claim 2, wherein a radius of curvature of eachraceway surface of said outer ring is set to be not less than 51.0% andnot more than 52% of a ball diameter, and a radius of curvature of theraceway surface of each of said inner ring is set to be not less than50.2% and not more than 51.2% of the ball diameter, respectively.
 5. Thebearing apparatus for supporting the pinion shaft according to claim 2,wherein an outer peripheral portion of said each seal is fixed to thetwo counter bores of said outer ring, and comprises a lip portion at aninner periphery having a shape for contacting to each shoulder portionof said two inner rings, and being able to be opened towards the outsideof the bearing.
 6. The bearing apparatus for supporting the pinion shaftaccording to claim 5, wherein the lip portion of the seal arranged on apinion gear side is compulsorily pressed to the shoulder portion of saidinner ring by means of a spring ring.
 7. The bearing apparatus forsupporting the pinion shaft according to claim 1, wherein an air flowportion for communicating an inside with an outside of said bearing isformed in said seal arranged on a counter-pinion gear side.
 8. A pinionshaft support apparatus, comprising: a pinion shaft having a pinion gearat one end and having a screw shaft portion at the other end; a doublerow angular contact ball bearing with vertex of contact angles outsideof bearing attached to an outside of a shank portion of said pinionshaft; and a nut which is screwed and fixed onto said screw shaftportion of said pinion shaft and integrates said double row angularcontact ball bearing with vertex of contact angles outside of bearingwith said pinion shaft, wherein said double row angular contact ballbearing with vertex of contact angles outside of bearing is filled withgrease in a bearing internal space sealed with seals equipped at bothends in a shaft direction.